We developed a series of transmembrane conjugated oligoelectrolytes (COEs) with tunable optical emissions from the UV to the near IR to address the false-positive problem when detecting nanometer-sized extracellular vesicles (EVs) by flow cytometry. The amphiphilic molecular framework of COEs is defined by a linear conjugated structure and cationic charged groups at each terminal site. Consequently, COEs have excellent water solubility and the absence of nanoaggregates at concentrations up to 50 μM, and unbound COE dyes can be readily removed through ultrafiltration. These properties enable unambiguous and simple detection of COE-labeled small EVs using flow cytometry with negligible background signals. We also demonstrated the time-lapsed tracking of small EV uptake into mammalian cells and the endogenous small EV labeling using COEs. Briefly, COEs provide a class of membrane-targeting dyes that behave as biomimetics of the lipid bilayer and a general and practical labeling strategy for nanosized EVs.

Membrane-intercalating conjugated oligoelectrolytes are emerging as versatile tools to modify or functionalize lipid bilayers. Through modular chemical design, this new molecular platform has applications in a range of biological fields.

This review examines recent advances in conjugated polyelectrolyte design and their applications in advanced optoelectronic and energy storage devices, emphasizing the performance benefits of their dual electronic and ionic transport mechanisms.